Field of the Invention
This invention is related to a process and system for converting crude oil into improved feedstock for steam cracking to produce chemical hydrocarbons and for a process and system for integrating a steam cracking feedstock preparation process with a steam cracking facility. More specifically this process can include process subsequences including an atmospheric distillation unit(s), vacuum distillation unit(s), cracking unit(s) and coking unit(s), all operated at conditions to produce feed materials for steam cracking superior to those generated in typical refinery operations.
Background
Conventional petroleum refinery configurations, selection and arrangement of processing units, are designed to provide optimum transportation fuels, not chemical feedstocks. Light products tend to be minimized as of lower economic value. Naphtha, for example, is usually converted by catalytic reformer to highly aromatic and branched paraffins useful as high octane transportation fuel. However, naphtha is also a valued source of chemical feedstock as it can be easily converted to olefins and aromatic by steam cracking. In general, therefore, petroleum refineries have not been configured to maximize chemical feedstocks. The present invention is a process configuration that minimizes conventional transportation fuel production and maximizes chemical feedstock and chemical-grade light olefins and aromatics (for example, ethylene, propylene, C4 mono-olefins, butadiene, benzene, toluene, xylene, ethylbenzene and styrene).
Before 2005 the price of crude ranged from about $15-$40/bbl and the price and availability of naphtha such that the differential value was about $30-$50/bbl. As a result it was not generally economic to upgrade crude oil to naphtha (and other steam cracker feeds). More recently the differential value of crude and naphtha has increased to $100-$200/bbl making the purchase of naphtha as a sole source of steam cracking (chemical feedstock production) far less attractive. Thus, intentional conversion of crude oil solely to steam cracker feedstock has become desirable. Providing special configurations of refining units to produce only chemical feedstocks is unique and not previously considered. Such configurations require careful selection and operation of conventional refining processes to produce unexpected results and economies.
There continues to be a need for more efficient processes and systems to convert crude oil to chemical feedstocks.